Friday, December 21, 2007

Perfume: The Story of DNA & Desire

The movie Perfume: The Story of a Murderer begins with scenes that are not for the faint - blood, maggots, vomit, vermin, rotten fish - foul sights, surely putrid smells. If you can stomach the intensity, the movie is about Jean-Baptiste Grenouille, a man who was born with an acute sense of smell. Driven to create a perfume that captures the essence of a woman, he obsessively pursues the perfect scent to the point that his obsession moves from creativity to murder.

Though fictional, the story symbolizes our species' fascination with scent - and perfumery. The practice of creating scents to apply to skin, hair, body, fabric and living space dates back as far as there has been written history. Perfumery began before anyone ever heard of the three wisemen who brought frankincense and myrrh for a certain baby. Rather than go into the history of perfumery, I'd like to introduce you to the science of it. It's one of my very favorite subjects!

Figuring out which scents appeal to the broadest base of people is one way that professional perfumers can maximize their profits. Another way is to somehow target scents to people who most like a particular scent or scent family. Although perfumers have been at it for along time, research into why people prefer the scents they do is just getting started.

You may have heard that most people like vanilla, and that is generally true, and that some people like ylang-ylang, but others hate it. The same goes for patchouli; it's hit-or-miss. What you may not know is that scientists have figured out that whether people like a scent has to do with their genetic makeup, specifically the part of it that codes for proteins on the surface of certain immune cells.

MHC is a stretch of DNA that creates proteins of the surface of immune cells that help the body recognize and differentiate 'self' from 'non-self.' MHC has profound implications for our ability to stay healthy, but research from Wedekind has also turned up some fascinating connections to its role in body odor, perfume preference and even mate selection.

MHC influences body odor. Don't ask me how it does, it just has to do with bacteria, armpits, and crotches. People can actually detect the subtle MHC-based differences in body odor, and when asked to sniff the worn shirts of potential 'dates' and 'mates,' people routinely choose as the "best smelling" those people whose MHC is different. Humans prefer a significant other whose genes are different. This makes good evolutionary sense. That combination would produce offspring who's immune system has a good chance of being able to detect a wider range of germs, thus being healthier.

Wedekind's team of scientists discovered that people who have the same genetic code for MHC like the same scents. It hasn't been studied yet, but it stands to reason that perfume preferences would "run in families." Are sisters and mothers genetically programmed to select the same aromatherapy products from Bath & Body Works? Not exactly. It's not like such convenience was available in the nature red in tooth and claw days (and nights) of our ancestors' time. But - Wedekind's research suggests that people select perfume and odors to augment their own naturally occurring odor and DNA.

Other lines of evidence suggests that we've been evaluating others' mate potential based on their scent (and consequently MHC, DNA) for a very long time. I think humans used various natural odors in ancestral times to augment body odor and still use it in modern times to make ourselves more appealing to the opposite sex. Wedekind's other research suggests that we choose and reject mates based in part on their body odor. And, a few studies have even found that choosing mates with the wrong MHC actually affects fertility.

Nowadays we manipulate our body odor to maximize our appeal to others and alter our mood. The mark of a true Darwinian winner is whether or not you actually choose artificial scents that match your MHC - and - whether you choose a partner to reproduce with who likes what you like, but only to a point.

Next time you look at the tiny flower sewn to the center piece of a brassiere, recognize it as the modern day version of a little satchel of fragrant roses, oils, and herbs that women once pinned between their breasts to perfume and provoke - desire.

I am actually awaiting word on funding for a project looking at MHC and mate choice in my study species right now! Not only does diverse MHC increase immune responses but choosing a mate with a different MHC type will help to avoid inbreeding (which my be linked to that decreased fertility you mentioned). Consdering the effects on mating and immunity, I am fascinated by the potential importance of MHC on conservation. Do you know of any MHC work on endagered primates?

About Me

I'm a papermaker, a newspaper editor, and have a PhD in primate social psychology — I guess you could say I am a paper expert! Toddler Field Notes and her two canine companions — both Newfoundlands — make frequent appearances here.